The present invention relates to security fences and specifically relates to security fences having electrical detection devices incorporated therein.
Fences have been in existence ever since man first wanted to keep something in or out of a specified area. Electrified fences have also been known for a long time, and these fences are generally of the kind in which the body contacting the fence receives an electrical shock, thus, being prevented from entering or exiting the fenced area. This fence was an improvement over the old barbed-wire fence used to fence the open range of the United States.
Presently, one of the most popular fences is the cyclone fence or chain-link fence, which is a relatively massive metal structure which physically prevents any passage through the fence. Electrification of this type of fence is somewhat cumbersome; however, U.S. Pat. No. 2,530,247 describes one manner in which this may be accomplished.
Another kind of fence, which may be thought of as being electrified, is the intrusion detection fence which utilizes coaxial cable or the like in combination with an oscillator or RF generator to create an electric field which is part of a tank circuit. The resonance of the tank circuit will change when the circuit is detuned by the proximity of the body of an intruder. The kind of security system normally is complicated and expensive and must also rely upon another fence, or security personnel, to provide the actual physical prohibition of the intruder. Cyclone fences and electronic intrusion detection systems are expensive when the perimeter of the area to be fenced is more than that normally associated with a private dwelling.